During electrolytic purification of water, a flow stream from a body of water is passed through an electrolytic cell or other chlorine-generating assembly to oxide halide ions of the water by electrolysis to form hypohalic acid, hypohalite ions or both to disinfect or “chlorinate” the water. The treated flow stream is then returned to the body of water.
Some assemblies for chlorinating water by electrolysis include a flow sensor that senses if water is flowing through the assembly. Such a flow sensor, sometimes referred to as a gas trap sensor, includes an electrode that detects flow so long as there is conductivity between the electrode and one of the chlorine-generating electrode plates of the chlorine-generating assembly. The electrolytic process generates gas bubbles that are pushed out of the assembly by the water flow. When water is not flowing through the assembly, the generated gas bubbles build up and break the connection between the gas flow electrode and the chlorine-generating electrode plates. However, in low flow situations, for example water flowing at a rate lower than approximately 30 gallons per minute (GPM), gas continues to build in the flow sensor faster than the water flow can push it out. The buildup of gas breaks the connection between the gas flow electrode and the chlorine-generating electrode plates and the flow sensor is unable to sense the water flow and erroneously returns a “no flow” condition even though water is flowing through the assembly.